CRUSTAL STRUCTURE IN THE PROFILE ACROSS CENTRAL JAPAN AS DERIVED FROM EXPLOSION SEISMIC OBSERVATIONS
CRUSTAL STRUCTURE IN THE PROFILE ACROSS CENTRAL JAPAN AS DERIVED FROM EXPLOSION SEISMIC OBSERVATIONS
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根据爆炸地震观测得出的日本中部剖面地壳结构
DOI：
10.4294/jpe1952.20.197
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发表时间：
1972
期刊：
影响因子：
--
通讯作者：
I. Furuya
中科院分区：
文献类型：
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作者：
H. Aoki;T. Tada;Yoshimi Sasaki;Tooru Ooida;I. Muramatu;H. Shimamura;I. Furuya
对日本中部靠近东经137°的剖面地壳结构的研究始于1966年，当时在阿图米半岛附近发生了20次爆炸。1967年，在专门为研究地壳结构而安排的陆地站点上，观察到诺托半岛附近发生了21次反向射击，在埃比苏矿场还发生了一次3吨重的爆炸。大多数台站都配备了磁带记录系统，这为我们提供了一种过滤技术来检测低S/N比的信号。通过过滤，记录质量大大提高，并揭示了以下特征：a.在阿图米半岛附近的爆炸中广泛观察到Pn波，而在日本海的爆炸中没有。b.在Noto半岛附近的爆炸中明显观察到属于花岗岩层的波，但在阿图米半岛外的爆炸中，除了半岛附近的枪击外，几乎没有或几乎没有观察到属于花岗岩层的波。这些显著的差异反映了剖面上地壳结构的不对称性。时间项方法对于日本海沉积物的提取是令人满意的，但对于莫霍面的提取却不是很理想。开发了一种利用长波分量的新方法，并在本研究中使用，从而产生了许多可能的结构。由此得到的地壳结构总体上是山地以下的大陆结构，太平洋下的海洋结构，以及日本海下的中间结构。图17显示了许多模型中最有可能的一个。重力数据也被用于选择最佳模型。玄武岩层的厚度尚不清楚，但在剖面的南半部应该很薄。它与距离仅220公里的东经139°剖面上的构造形成了鲜明的对比。阿图米半岛附近的爆炸还获得了上地幔的速度梯度。
Studies on the crustal structure in the profile across central Japan close to the longitude 137°E were started in 1966 with 20 explosions made off the Atumi Peninsula. In 1967, twenty-one reverse shots off the Noto Peninsula and a supplementary three-ton explosion at the Ebisu Mine were observed at stations on land specially arranged for the derivation of crustal structure. Most of the stations were equipped with magnetic-tape-recording systems which provide us a filter technique to detect signals of low S/N ratio. The quality of record was extensively increased through filtering, and the following characteristic features were revealed:A. Pn waves were extensively observed in the explosions off the Atumi Peninsula but not in those in the Sea of Japan.B. Waves belonging to a granitic layer were clearly observed in the explosions off the Noto Peninsula but were absent or almost absent in the explosions off the Atumi Peninsula except for shots near the peninsula. These marked differences suggest an asymmetric crustal structure in the profile.A time-term method is satisfactory for the derivation of sediments under the Sea of Japan, but not for the derivation of the Moho discontinuity. A new method utilizing long wave components, was developed and used in the present study resulting in many possible structures. The crustal structures thus obtained are, in general, continental under the mountain area, oceanic under the Pacific, and intermediate under the Sea of Japan. The most probable one out of many is shown Fig. 17. Gravity data were also used in the selection of the best model. The thickness of the basaltic layer remains unknown, but it should be very thin in the southern half of the profile. It forms a striking contrast with the structure in the profile along the longitude 139°E which is located within a short distance of only 220km.A velocity gradient for the upper mantle was also obtained from the explosions off the Atumi Peninsula.